The present invention relates generally to molecular compounds which encode the protective M-like protein of Streptococcus equi (SeM), the amino acid compound which is thereby encoded, and compositions of matter which incorporate either the encoding compounds or the cellular components for which they encode. For instance, vaccines which utilize the amino acid compounds or vectors and cell lines useful to make the amino acid compounds described herein are subjects of the present invention. The present invention provides methods to stimulate S. equi-specific immune response in horses. It also provides diagnostic assays for Streptococcus equi. 
Streptococcus equi, a Lancefield group C streptococcus, causes strangles, a highly contagious disease of the nasopharynx and draining lymph nodes of Equidae. The 58 kDa antiphagocytic M-like protein (SeM) is a major virulence factor and protective antigen and functions by limiting deposition of C3b on the bacterial surface and by directly binding fibrinogen. Boschwitz and Timoney, 17 Microbiol. Pathogenesis 121 (1994) and Boschwitz and Timoney, 62 Infect. Imnun. 3515 (1994).
In the recent past, S. equi outbreaks on horse farms have been avoided and treated by quarantine of suspect animals; antiseptic handling of food, bedding and housing; and antibiotics when indicated. Vaccines comprising avirulent S. equi or fractions thereof have been described, but success rate has been low. U.S. Pat. No. 5,183,659 describes a vaccine which stimulated a nasopharyngeal antibody response in horses, but the vaccine had a limitation of many such vaccines, which is risk of reversion to virulence and occasional abcess development in vaccinated horses.
S. equi is shed in nasal discharges and pus from lymph nodes of affected animals. Routine laboratory detection of the bacterium involves bacteriologic culture of nasal swabs, nasal washes and pus from abscesses and is often difficult because of background contamination, small numbers of the organism, or the presence of S. zooepidemicus and other xcex2-hemolytic streptococci. Completion of culture and identification usually takes 2 to 3 days, an excessively lengthy interval given the highly contagious nature of strangles and the need to quickly identify shedding horses so that they may be isolated in the early stages of an outbreak.
It is an object of the present invention to provide molecular compounds which encode SeM and compositions of matter which incorporate either the encoding compounds or the cellular components for which they encode.
It is therefore an object to provide vectors, cell lines and cell membrane preparations using the compounds disclosed.
It is yet another object to provide a method to provide assays for detection of Streptococcus equi. 
Other objects and features of the present invention win be apparent from the following detailed description, examples and claims.
Definitions
As used herein, the following terms shall have the corresponding meaning set forth. All other terms are intended to have the meaning as understood commonly by those in the relevant field of art.
xe2x80x9cBiological Samplexe2x80x9d means nasal or oral mucus sample or blood sample.
xe2x80x9cTransformationxe2x80x9d and xe2x80x9ctransfectionxe2x80x9d mean to cause nucleic acid to enter a cell, whether or not the nucleic acid incorporates into the genome.